12. Warning in line 1 at character 938: The value for "href" is not in a valid or recognizable form such as http://, https://, ftp://, gopher://, nntp://, telnet://, wais://, javascript:, mailto:, news:, etc. Please ensure that it is correct.
Which has this note: Using custom scheme URLs? Custom scheme URLs continue to be supported, although they are not recommended. You can declare them as rel=alternate elements either in the head of the HTML page or in the sitemap. Associate your site and app in Search Console so Google can crawl your sitemap for App Indexing.
So I would not use them... but I will probably change it so that CSS HTML Validator ignores them just in case they are used.
Albert Wiersch wrote: ↑Mon Oct 02, 2017 9:13 am
...Which has this note: Using custom scheme URLs? Custom scheme URLs continue to be supported, although they are not recommended. You can declare them as rel=alternate elements either in the head of the HTML page or in the sitemap. Associate your site and app in Search Console so Google can crawl your sitemap for App Indexing.
So I would not use them... but I will probably change it so that CSS HTML Validator ignores them just in case they are used.
It's a bit confusing, is the originally posted <link rel="alternate" valid or not? If not recommended, than what is an alternative? Do you know?
Notice the "/http/" part which specifies http as the scheme, which is not a custom scheme.
Your scheme uses https. I'm not sure if that is considered a "custom scheme" or not since it is not "http".
Unfortunately I don't want to give any further recommendations because my understanding of all this is fairly new and basic.
I can only recommend that you study some of the links posted in this thread and try to find some other ones. Sorry I can't be more helpful here but I was able to change the config file to suppress those warnings based on the examples in some of the provided links.